I don't want to light the candles though, I just want to either drink or remove the liquid from the goblet before testing what moving one candle does, since I don't think lighting it will do much - Doc clearly said that "Moving these items will also moves the hooks and whatever mechanism they are part of."
So yes, moving those items will most likely open the coffins, as they are sealed shut, implying you can't open them normally, and this seems too much of a coincidence. Lighting candles is a good idea, but since MaxFulvus has already found a mechanism, I doubt it will do much - and since the sarcophagi are sealed shut, any corporeal undead won't get out until you open it (move the candles/goblet), and I doubt if it's wights/ghosts they'd wake up due to candles, since the paladins nor cleric didn't get any feeling about them, so they aren't magical.
Also since they're attached to the altar by hooks, I doubt there's an additional level of having an exploding gas trap inside the sarcophagi etc. - as it'd also explode the Undead inside. Poison gas is a valid point, but I don't think it's probably going to be inside them. I think it's most likely going to be corporeal undead, and they're going to wake up once you open the sarcophagi. There might even be some interesting treasure inside!
However moving the goblet might release a trap, as I think each candle opens one sarcophagus and the goblet will most likely be protected if it's beneficial. Lifthrasil: Green Hilltop has a point. Correction:
Thras, dwarven mage, lights the candles one at a time. Waiting a bit before lighting the second. THEN we try to move the candles. And then, if nothing happens, I try to take the goblet.
Knowing the DM, he will probably do all the actionsyou've listed at once in one post (as that's the way how it sounds from how you described it), so you're gonna have the effects of everything - and so far, Babark is trying to destroy the altar by casting Melt Stone, which will either (depending on how the mechanism works)
a) activate the mechanism
b) not activate the mechanism and disable it from working ever again
So I recommend if you want to try to drink the liquid, do it first, so he doesn't end up melting the altar before you get to it (after all the waiting with the candles), or saying you rush forward to catch the goblet before it spills when you notice him casting the spell, if it's possible (due to being attached to the altar) or just chugging it as the stone melts. And avoiding any traps that destroying the altar might spring.
If we had time (Babark not destroying the altar), I think the best course of action is to make a makeshift straw, and drink liquid out of it, thus not triggering the mechanism and having time enough to run to Roark for the cure poison potions, if he's willing to share it, in case the drink is poisoned. (it might be both poisoned and giving beneficial results).
And then experiment with the candles.